The type of clasp commonly known as the "D-ring" comprises two rings secured to a common or looped end of a strap and another strap is releasably fastened to the rings by threading the other strap through both rings, then doubling back through one ring so that the other strap is frictionally retained between the rings. This device has seen many applications, adaptations and improvements since its introduction in the late 1800's. An early approach to a fastener of this type is described in U.S. Pat. No. 395,965 to Ferris, which discloses a clasp comprising two wire loops which hold the tape of a stocking supporter threaded therethrough. U.S. Pat. No. 1,393,881 to Burg describes a belt buckle of similar operation wherein the wire loops have a rectangular, rather than rounded configuration. Other forms and uses for the basic D-ring type fastener are further illustrated in U.S. Pat. Nos. 655,882 to Maxwell and 1,484,680 to Stoddard et al.
Presently, the D-ring is commonly used as an adjustable clasp for straps, belts, webbing and the like. For example, U.S. Pat. No. 4,044,400 to Lewicki et al discloses its use as a part of a helmet retention system. When used for this purpose, however, the standard D-ring is in many ways inconvenient and difficult to manipulate both in threading or fastening the strap; and once threaded and tightened, the rings cannot be easily loosened or expanded without the use of both hands. The procedure is further complicated if the hands or strap is wet, or if the cyclist is wearing gloves, as is often the case. Moreover, in the event of accident or emergency, it may be necessary for the wearer or rescuer to remove the helmet quickly. For instance, in the fastener of Lewicki et al, which is provided with a pull-tab for easier grasping, quick and complete release of the strap cannot be effected with one hand without considerably dexterity on the part of the wearer. Another problem associated with fasteners of the loop or D-ring type is the difficulty of applying sufficient leverage to release the strap once tightened in place, since the releasing force must be applied at or adjacent to the fastening of the strap to the ring.